Wireless-based aircraft data communication system with automatic frequency control

ABSTRACT

A system and method for providing a retrievable record of the flight performance of an aircraft is disclosed and includes a ground data link unit that obtains flight performance data representative of aircraft flight performance during flight of the aircraft. An archival data store is operative to accumulate and store flight performance data during flight of the aircraft. A spread spectrum transceiver is coupled to the archival data store and includes a transmitter that is operative after the aircraft completes its flight and lands at an airport to download the flight performance data that has been accumulated and stored over one of a plurality of sub-band frequency channels of a spread spectrum communication signal. The frequency is chosen based upon the position of the aircraft determined by an onboard global positioning system. An airport based spread spectrum receiver receives the spread spectrum communication signal from the aircraft and demodulates the signal to obtain the flight performance data.

FIELD OF THE INVENTION

This invention relates to a system and method for providing aretrievable record of the flight performance of an aircraft and forexchanging information to and from an aircraft, and more particularly,this invention relates to a system and method for providing aretrievable record of the flight performance of an aircraft and forexchanging information to and from an aircraft using automatic frequencychannel selection.

BACKGROUND OF THE INVENTION

In U.S. patent application Ser. No. 09/474,894, entitled "WIRELESSGROUND LINK-BASED AIRCRAFT DATA COMMUNICATION SYSTEM WITH ROAMINGFEATURE," filed Jun. 2, 1999, which is a continuation of parentapplication Ser. No. 08/557,269, filed Nov. 14, 1995, U.S. Pat. No.6,047,165 and entitled, "WIRELESS, FREQUENCY-AGILE SPREAD SPECTRUMGROUND LINK-BASED AIRCRAFT DATA COMMUNICATION SYSTEM," the disclosureswhich are hereby incorporated by reference in their entireties, a grounddata link system provides a wireless mechanism for transferring datafiles to and from aircraft while the aircraft is on the ground at grounddata linked equipped airports. In the wireless ground link-basedaircraft data communication system with this roaming feature, theretrievable records of the flight performance of an aircraft aredownloaded using the ground data link unit. The ground data link unitincludes an archival data store operative to accumulate and store flightperformance data during flight of the aircraft. A spread spectrumtransceiver is coupled to the archival data store and includes atransmitter that is operative after the aircraft completes its flightand lands at an airport to download the flight performance data that hasbeen accumulated and stored by the archival data store during flightover one of a plurality of sub-band frequency channels of a spreadspectrum communication system.

An airport based spread spectrum transceiver includes a receiver thatreceives the spread spectrum communication signal from the aircraft anddemodulates the signal to obtain the flight performance data. Theairport based spread spectrum transceiver includes a probe transmissioncircuit that transmits a probe beacon on each sub-band frequency channelto the spread spectrum transceiver to determine which sub-band frequencychannel is preferred. The probe beacon could include an interrogationsignal that contains data representative of an allowable power limit ofthe spread spectrum communication signal that can be transmitted.

Based upon the probe beacon, the aircraft can select a particularsub-band frequency channel. However, it would be more advantageous ifthe aircraft ground data link unit could select a sub-band frequencychannel automatically based upon a specified parameter that could belocated or known, depending on the position of the aircraft.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a systemand method for providing a retrievable record of the flight performanceof an aircraft where sub-band frequency channels of a spread spectrumcommunication signal can be selected based on the position of theaircraft without analyzing a probe beacon that is transmitted from theground.

In accordance with the present invention, a system provides aretrievable record of the flight performance of an aircraft and includesa ground data link unit that obtains the flight performance datarepresentative of aircraft flight performance during flight of theaircraft. The ground data link unit includes an archival data storeoperative to accumulate and store flight performance data during flightof the aircraft. A spread spectrum transceiver is coupled to thearchival data store and includes a transmitter that is operative afterthe aircraft completes its flight and lands at an airport to downloadthe flight performance data that has been accumulated and stored duringflight over one of a plurality of sub-band frequency channels of thespread spectrum communication signal. The sub-band frequency channel ischosen based on a position of the aircraft determined by an onboardglobal positioning system in order to comply with any regulatoryfrequency requirements of the geographical area in which the aircrafthas landed. The airport based spread spectrum receiver receives thespread spectrum communication signal from the aircraft and demodulatesthe signal to obtain the flight performance data.

In a further aspect of the present invention, the ground data link unitincludes an adaptive power control unit that varies the emitted powerlevel of the spread spectrum communication signal based on the positiondetermined by the onboard global positioning system in order to complywith any regulatory power requirements of the geographical area in whichthe aircraft has landed. The ground data link unit includes a controllerand memory having a record of a plurality of geographical areas and anemitted power level to be used in each respective geographical area. Theground data link unit includes a controller and memory file having arecord of a plurality of geographical areas and a respective sub-bandfrequency channel to be used in each respective geographical area. Theairport based archival data store coupled to the airport based spreadspectrum receiver receives and stores the flight performance data. Awireless router can couple the airport based spread spectrum receiver tothe airport based archival data store. The airport based server iscoupled to the airport based spread spectrum receiver and receives theflight performance data from the airport based spread spectrum receiver.A remote flight operations center can be operatively coupled to theairport based server for receiving and processing retrieved flightperformance data.

In still another aspect of the present invention, the spread spectrumcommunication signal includes a direct sequence spread spectrum signal.The spread spectrum communication signal includes a signal within the Sband. The spread spectrum communication signal includes a signal withinthe range of about 2.4 to about 2.5 GHz. The archival data store of theground data link unit further comprises a circuit for compressing theflight performance data during flight of the aircraft.

In still another aspect of the present invention, a plurality of sensorscan be located throughout the aircraft for sensing routine aircraftconditions and generating parametric data, such as received by a flightdata recorder, representative of the aircraft flight performance duringflight of the aircraft. A global positioning system is positionedonboard the aircraft and generates position data reflective of thelatitude and longitude of the aircraft. A multiplexer is connected tothe plurality of sensors and global positioning system for receiving theparametric data and position data and multiplexing the parametric dataand position data determined by the global positioning system.

The ground data link unit is connected to the multiplexer for receivingand multiplexing a sample of the multiplexed stream of parametric dataand position data. The ground data link unit includes the archival datastore and spread spectrum transceiver having a transmitter to downloadthe flight performance data to the airport based spread spectrumreceiver.

In still another aspect of the present invention, a system and method ofthe present invention can exchange information to and from an aircraft.The spread spectrum transceiver includes a receiver that uploads dataover a second spread spectrum communication signal from an airport basedspread spectrum transmitter, which transmits data for uploading to theaircraft over the second spread spectrum communication signal. Thisuploaded data can include video, audio and flight information that hasbeen stored within the airport based archival data store. The video,audio and flight information to be uploaded to the aircraft includesdigitized in-flight passenger service and entertainment video and audiofiles.

A method aspect is also disclosed and includes the step of collectingdata within a ground data link unit on the flight performance of theaircraft during flight of the aircraft. The method also includes thestep of accumulating and storing within an archival memory of the grounddata link unit the flight performance data during flight of theaircraft. The method also comprises the step of determining the positionof the aircraft based on the global positioning system, and after theaircraft lands in the airport at completion of the flight, selecting asub-band frequency channel based on the determined position of theaircraft to comply with any regulatory frequency requirements of thegeographical area in which the aircraft has landed. The method alsocomprises the step of downloading the flight performance data that hasbeen accumulated and stored during the flight over the selected sub-bandfrequency channel of a spread spectrum communication system to anairport based spread spectrum receiver where the communication signal isthen demodulated to obtain the flight performance data.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent from the detailed description of the invention whichfollows, when considered in light of the accompanying drawings in which:

FIG. 1 is a drawing showing a representative gate system of an airport.

FIG. 2 is a drawing illustrating a minimum air space separation foraircraft on a federal airway.

FIG. 3 is a plan diagram of a typical airport traffic pattern.

FIG. 4 is a bar chart illustrating the number of near mid-air collisionsbetween 1992 and 1997.

FIG. 5 is a schematic diagram showing the ground coverage cell and anairborne coverage cell.

FIG. 5A is a frequency spectrum graph for a single ground coverage celland a single airborne coverage cell.

FIG. 6 is a schematic diagram illustrating how en route aircraft can actas repeaters to extend the communication range of a ground-basednetwork.

FIG. 6A is a cross-section of an example of a jet engine that generatesengine events to be transferred from the ground data link unit of thepresent invention while en route after initial aircraft take-off.

FIG. 6B is a chart showing various jet engine event reports at enginestart.

FIG. 7 is a schematic diagram of an omni-directional antenna providingboth ground and air coverage that can be used with the presentinvention.

FIG. 8 is a block diagram illustrating the use of the ground data linkunit of the present invention with various end nodes.

FIG. 9 is a detailed schematic drawing showing the interconnection of anairport network and ground data link network.

FIG. 10 is a flow chart showing basic file transfer.

FIG. 11A is a schematic drawing that shows an example of an airbornesystem acting as a mobile node on its own home subnet and a foreignagent for other mobile nodes.

FIG. 11B is a schematic drawing that shows an example of an airbornesystem acting as its own foreign agent on a foreign subnet and a foreignagent for other mobile nodes.

FIG. 12 is a block diagram showing the basic elements of a ground datalink unit.

FIG. 13 is another block diagram of another part of the ground data linkunit showing various components.

FIG. 14 is a block diagram illustrating basic components of the grounddata link aircraft unit.

FIG. 15 is another block diagram of the ground data link unit of thepresent invention showing greater detail of the interconnection withflight management computers and on board GPS system.

FIG. 16 is a more detailed block diagram of a type of spread spectrumtransceiver that can be used with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Harris Corporation of Melbourne, Fla. is a manufacturer of Ground DataLink (GDL), such as disclosed in copending and allowed patentapplication Ser. No. 08/557,269, filed Nov. 14, 1995, and entitled"WIRELESS, FREQUENCY-AGILE SPREAD SPECTRUM GROUND LINK-BASED AIRCRAFTDATA COMMUNICATION SYSTEM," the disclosure which is hereby incorporatedby reference in its entirety. In the GDL, the system provides a wirelessmechanism for transferring data files to and from air transport aircraftwhile they are on the ground at ground data link equipped airports. Theground data link is designed to support multiple airline applications,such as flight safety, engineering and maintenance, and passengerservices.

In one basic application of the system and method of the invention, aground data link unit obtains flight performance data representative ofaircraft flight performance during flight of the aircraft. This type ofdata could be that data that is conventionally forwarded to the "blackbox" used in an aircraft. Different sensors receive telemetry data,which is multiplexed and sent serially to the GDL unit.

An archival data store is operative to accumulate and store flightperformance data during flight of the aircraft. A wideband spreadspectrum transceiver is coupled to the archival data store and includesa transmitter that is operative after the aircraft completes its flightand lands at an airport to download the flight performance data that hasbeen accumulated and stored by the archival data store during flightover a wideband spread spectrum communication signal. An airport basedwideband spread spectrum transceiver includes a receiver that receivesthe wideband spread spectrum communication signal from the aircraft anddemodulates the signal to obtain the flight performance data. In oneaspect of the invention, an adaptive power control unit varies theemitted power level of the wideband spread spectrum communication signalbased upon the geographic location of the airport. In still anotheraspect of the invention, the airport based spread spectrum transceiverincludes a probe transmission circuit that transmits a probe beacon oneach sub-band frequency channel approved for use by the regulatory bodyof that country to the spread spectrum transceiver of the ground datalink unit to determine which sub-band frequency channel is preferred.The fixed ground-based spread spectrum transceiver can be operative toselect desired sub-band frequency channels and dynamically assign suchsub-band frequency channels based upon the measured signal quality oneach approved frequency and channel for the geographic location of theairport.

An airport based archival data store can also be coupled to the airportbased wideband spread spectrum transceiver that receives and stores theflight performance data. An airport based processor can be coupled tothe archival data store for retrieving flight performance data from theairport based archival data store for further processing. A remoteflight operations control center can also be operatively coupled to thebase station to download the flight performance data.

The present invention provides an improvement with advantageous featuresover the general system as disclosed in the copending and incorporatedby reference '269 patent application identified above. In one aspect,the ground data link can be used in an aircraft, automobile or similarvehicle. Transmit power and frequency can be automatically adjusted tocomply with the regulatory requirement of the country or area where thetransceivers operate. The system can use a location sensing device todetermine latitude and longitude, such as a global positioning system(GPS) receiver technology. The system is advantageous because it enablesmobile units to use location information to control transmit power andfrequency, as opposed to information transmitted within a fixed, groundbased probe message.

The ground data link transceiver can also be used in an air-to-groundapplication, where the range is about 21 miles. The on-groundapplication uses data rates ranging from about 1 to 11 Mbps fordownloading, from the aircraft, files such as electronic maintenance logbooks, cabin maintenance logs, weight and balance reports and flightdeck computer results. During in flight, only a number of functions aretransmitted and it is possible to reduce the data rate from the initialrange of about 355 Kbps to improve the communication range of thenetwork without adversely impacting throughput. Data rate can be variedto accommodate the amount and priority of data, based on the requireddistance. An example of a spread spectrum transceiver that can be usedfor the present invention, and provides data rates as high as 11 Mbps,is the type disclosed in commonly assigned U.S. patent application Ser.No. 08/819,846, filed Mar. 17, 1997, to Snell.

Additionally, engine events are sensed and stored not only in thearchival storage during flight of an aircraft, but also downloadedduring the first 30 seconds of take-off and/or during initial climb.Thus, it is possible for a maintenance crew or other flight operationscontrol center to obtain data during initial take-off and climb to aidin determining whether engine maintenance would be required at thedestination station. It is also possible to download OOOI times of anaircraft. Additionally, data such as the weight of the remaining fuelcan be downloaded and used for refueling planning. Last minute changesin gate assignment can be uploaded. En route wind and temperature datacan be downloaded and used to enhance the flight planning of subsequentflights over the same route.

The present invention is also advantageous because aircraft using theGDL network can act as wireless repeaters. Planes can be spaced five orten miles apart and the wireless communication system of the presentinvention can be extended, depending on the range of various airplanes.When aircraft leave and arrive as often as every 45 seconds, anair-to-air repeater network, in accordance with the present invention,can extend the network conductivity between aircraft and the groundnetwork. This can also enhance scheduling and airline maintenance.

Referring now to FIG. 12, there is shown a representative example of anoverall system architecture of a wireless ground link-based aircraftdata communication system used with the present invention. Thearchitecture has three interlinked subsystems: (1) an aircraft-installedground data link (GDL) subsystem 100; (2) an airport-resident groundsubsystem 200; and (3) a remote airline operations control center 300.The aircraft-installed ground data link (GDL) subsystem 100 includes aplurality of GDL airborne segments 101, each of which is installed inthe controlled environment of the avionics compartment of a respectivelydifferent aircraft. Each GDL airborne segment 101 is operative tocommunicate with a wireless router (WR) segment 201 of theairport-resident ground subsystem 200 through a wireless communicationslink 120.

The wireless router segment 201 routes the files it receives from theGDL airborne segment 101, either directly to the airport base station202 via the wired Ethernet LAN 207, or indirectly through local areanetworks 207 and airport-resident wireless bridge segments 203. Thewireless communication link 120 can be a spread spectrum radio frequency(RF) link having a carrier frequency lying in an unlicensed portion ofthe electromagnetic spectrum, such as within the 2.4-2.5 GHz S-band.

As will be described, once installed in an aircraft, the aircraft unit(AU) 102 of a GDL segment 101 collects and stores flight performancedata generated on board the aircraft during flight. It also stores anddistributes information uploaded to the aircraft via a groundsubsystem's wireless router 201, which is coupled thereto by way of alocal area network 207 from a base station segment 202 of a groundsubsystem 200 in preparation for the next flight or series of flights.

The uploaded information, which may include any of audio, video anddata, typically contains next flight information data, such as a flightplan, dispatch release, or load manifest, and uploadable softwareincluding, but not limited to, a navigation database associated with theflight management computer, as well as digitized video and audio filesthat may be employed as part of a passenger service/entertainmentpackage.

The ground subsystem 200 includes a plurality of airport-resident GDLwireless router segments 201, one or more of which are distributedwithin the environments of the various airports served by the system. Arespective airport wireless router 201 is operative to receive andforward flight performance data that is wirelessly down linked from anaircraft's GDL unit 101 to supply information to the aircraft inpreparation for its next flight, once the aircraft has landed and is incommunication with the wireless router. Each ground subsystem wirelessrouter 201 forwards flight files from the aircraft's GDL unit andforwards the files to a server/archive computer terminal 204 of theaircraft base station 202, which resides on the local area network 207of the ground subsystem 200.

The airport base station 202 is coupled via a local communications path207, to which a remote gateway (RG) segment 206 is interfaced over acommunications path 230, to a central gateway (CG) segment 306 of aremote airline operations control center 300, where aircraft data filesfrom various aircraft are analyzed. As a non-limiting example, thecommunications path 230 includes an ISDN telephone company (Telco) landline, and the gateway segments include standard LAN interfaces. However,it should be observed that other communication media, such as asatellite links, for example, may be employed for groundsubsystem-to-control center communications without departing from thescope of the invention.

The flight operations control center 300 includes a system controller(SC) segment 301 and a plurality of GDL workstations (WS) 303, which areinterlinked to the systems controller 301 via a local area network 305.Flight operations and flight safety analysts are allowed at controlcenter 300 to evaluate the aircraft data files conveyed to the airlineoperations control center 300 from the airport base station segments 202of the ground subsystem 200.

The respective GDL workstations 303 may be allocated for differentpurposes, such as flight operations, flight safety ,engineering/maintenance or passenger services. As described brieflyabove, the server/archive terminal 204 in the base station segment 202is operative to automatically forward OOOI reports downloaded from anaircraft to the flight control center 300; it also automaticallyforwards raw flight data files.

The system controller 301 has a server/archive terminal unit 304 thatpreferably includes database management software for providing forefficient transfer and analysis of data files, as it retrievesdownloaded files from a ground subsystem. As a non-limiting example,such database management software may delete existing files from a basestation segment's memory once the files have been retrieved.

Referring now to FIG. 13, a respective GDL segment 101 isdiagrammatically illustrated as comprising a GDL data storage andcommunications unit 111 (hereinafter referred to simply as a GDL unit)and an associated external airframe (e.g., fuselage) mounted antennaunit 113. In an alternative embodiment, antenna unit 113 may housediversely configured components, such as spaced apart antenna dipoleelements, or multiple, differentially (orthogonally) polarized antennacomponents.

The GDL unit 111 is preferably installed within the controlledenvironment of an aircraft's avionics compartment, to whichcommunication links from various aircraft flight parameter transducers,and cockpit instruments and display components, shown within brokenlines 122, are coupled. When so installed, the GDL unit 111 is linkedvia an auxiliary data path 124 to the aircraft's airborne dataacquisition equipment 126 (e.g., a DFDAU, in the present example). TheGDL unit 111 synchronizes with the flight parameter data stream from theDFDAU 16, and stores the collected data in memory. It is also coupledvia a data path 125 to supply to one or more additional aircraft units,such as navigational equipment and/or passenger entertainment stations,various data, audio and video files that have been uploaded from anairport ground subsystem wireless router 201.

The airborne data acquisition unit 126 is coupled to the aircraft'sdigital flight data recorder (DFDR) 128 by way of a standard flight datalink 129 through which collected flight data is coupled to the flightdata recorder in a conventional manner.

As described briefly above, and as diagrammatically illustrated in FIGS.13 and 14, the GDL unit 111 can be a bidirectional wireless (radiofrequency carrier-based) subsystem containing a processing unit 132 andassociated memory or data store 134, serving as both an archival datastore 134a and a buffer 134b for airline packet communications asdescribed below. The memory 134 is coupled to the DFDAU 126, via datapath 124, which is parallel to or redundant with the data path to theflight data recorder 128. Processing unit 132 receives and compressesthe same flight performance data that is collected by the aircraft'sdigital flight data recorder, and stores the compressed data inassociated memory 134. A report can be generated by the processing unit132, that includes many items of data, such as the flight number/leg andtail number/tray number of the aircraft and the appropriate OOOI time.

To provide bidirectional RF communication capability with a wirelessrouter 201, the GDL unit 111 includes a wireless (RF) transceiver 136,which is coupled to the antenna unit 113.

As will be described, on each of a plurality of sub-band channels of theunlicensed 2.4-2.5 GHz S-band segment of interest, a wireless router 201could continuously broadcast an interrogation beacon that containsinformation representative of the emitted power level restrictions ofthe airport. Using an adaptive power unit within its transceiver, theGDL unit 111 on board the aircraft could respond to this beacon signalby adjusting its emitted power to a level that will not exceedcommunication limitations imposed by the jurisdiction governing theairport. The wireless (RF) transceiver 136 then accesses the report datafile (such as OOOI) stored in memory 134, encrypts the data andtransmits the file via a selected sub-channel of the wireless groundcommunication link 120 to wireless router 201.

The recipient wireless router 201 forwards the report data file to thebase station segment temporarily until the report file can beautomatically transmitted over the communications path 230 to the remoteairline flight operations control center 300 for analysis. As shown inFIG. 15, the CPU can receive multiplexed telemetry data from multiplexer150. An on-board GPS system 152 can provide latitude/longitude data 154,which is used for the adaptive power control and frequency channelselection based on geographical area, as described above. First andsecond flight management computers 160, 162 can also be updated withfiles and verified as accurate by first and second Control Data Units(164, 166) as described below. Further details of the associatedcomponents are described in the above-identified and incorporated byreference '269 application.

Air Traffic Control (ATC) at busy airports requires that aircraftoperate under Instrument Flight Rules (IFR) to comply with a "gatesystem," which provides lateral separation between arriving anddeparting aircraft. FIG. 1 is one type of gate system of an aircraft,which in this example, is located in Calgary. Aircraft entering theairspace enter along the Standard Terminal Arrival Routes (STAR), shownin a dotted line. Departing aircraft are vectored to exit the airspaceon one of the outbound Standard Instrument Departure (SID) gates, shownin solid, circular arc lines. The actual departure gate assigned is thegate that is closest to the route of a flight.

Once a departing aircraft exits the airport airspace under thejurisdiction of the airport ATC, it proceeds along a course consistentwith its flight plan as filed with the ATC. Aircraft operating under IFRtravel along the centerline of a defined federal airway or on a routethat is a direct course between the conventional navigational aids (VORor TACAN) that define that route, as known to those skilled in the art.Aircraft periodically report the exact time they pass over variousnavigation aids so that the ATC can monitor the progress of the aircraftrelative to its flight plan and other aircraft. The ATC typicallymanages safe aircraft separation along these defined routes to fivenautical miles horizontally and 1,000 feet vertically, as shown in FIG.2, where aircraft 10 are shown spaced horizontally and vertically.

FIG. 3 illustrates an example of an airport traffic pattern for a givenrunway. The turn from base leg to final approach is at least 1/4 milefrom the runway. The traffic pattern altitude is typically 1,000 feetabove ground level. As illustrated, the aircraft 10 initially startsfrom a gate 12 and then proceeds to the different points labeled 1-6.The aircraft 10, as noted before, turns from the base leg to the finalapproach that is at least 1/4 mile from the runway. At point 3, it thenenters the runway 14 and at its departure indicated at point 4, theaircraft proceeds in a given direction as indicated at points 5 and 6.

As a result of air traffic congestion, particularly on routes in and outof busy airports, the minimum separation distances shown in FIG. 2 arefrequently typical separation distances maintained among en routeaircraft. As an example of the importance of maintaining safe en routeaircraft spacing, FIG. 4 shows the number of near midair collisionsreported between 1992 and 1997. Some near midair collisions, includingthose which may involve unsafe conditions, may not be reported becausepilots fail to see another aircraft or do not perceive accurately thedistance from another aircraft due to restricted visibility or therelative angle of approach. Other pilots may not report "near misses"because they fear a penalty or are not aware of the standard NMACreporting system. Industry experts have always been studying differentproposals that increase traffic density without affecting flight safety.Pilots have been surveyed about the safety effect of reducing theseparation minimums managed by ATC.

FIG. 15 illustrates a more detailed drawing of the ground data link unitwhere a server interface unit 320 and network server unit 322 are used.FIG. 15 explains how packets can be routed from one aircraftserver/router to another aircraft and can be used for country roamingand flight management computer uploads. As illustrated, the serverinterface unit 320 of the ground data link unit performs dataacquisition and receives telemetry data 324 such as the vehicle sensordata obtained from the plurality of sensors located throughout theaircraft or other vehicle in which the ground data link unit ispositioned. An onboard global positioning system 326 can generate thelatitude/longitude data 328, which can be multiplexed with the vehiclesensor telemetry data within the multiplexer 330. The server interfaceunit 320 includes a central processing unit 332 and a memory buffer 334that acts as a buffer with a LAN adaptor 336, similar to an Ethernetcard adaptor. The Server Interface Unit 320 can also provide interfacein both directions, such as for allowing uploading to a first flightmanagement computer 338 and a second flight management computer 340 andappropriate control display units 342, 344. Other aircraft avionics data346 can be downloaded.

The Network Server Unit 322 includes a LAN adaptor 350 that connects fortwo-way communication with the LAN adaptor 336 of the server interfaceunit 320. A server/router 352 connects to the LAN adaptor 350, and inturn, connects to the data store 134 that includes the non-volatilememory or archival data store 134a that could be a hard drive and thebuffer 134b. The server/router 352 also connects to the radio frequencycommunication transceiver 136, which also acts as a wireless LAN adaptoras described before. The RF communication transceiver 136 connects intoother aircraft and ground radio frequency transceivers 353 as notedabove. The server/router can also connect to another LAN adaptor 354,which in turn, provides two-way communication to the flight deck/cabinpersonal computers 356.

Referring now to FIG. 16, there is illustrated greater details of thespread spectrum communication transceiver 136 that illustrates basicelements. As shown in FIG. 16, an omni-directional antenna 360 can beused on the ground to provide gain for both the airborne and groundbased applications. An external LNA/PA 362 connects into an internalLNA/PA 364 that allows two-way communication with the radiofrequency/intermediate frequency (RF/IF) up/down converter 366.

A dual frequency synthesizer 368 works in conjunction with a quadraturedirect sequence spread spectrum (DSSS) modem 370. A switchedintermediate frequency band pass filter 372 is operative with the RF/IFup/down converter 366 and the quadrature DSSS modem 370. A tunable lowpass filter 374 is operative with the quadrature DSSS modem as output.The switched IF band pass filter 372 and tunable low pass filter 374 actto reduce filter bandwidths and improve the signal/noise radio andincrease communication range when the PN chipping rate and data rate isreduced. Data is transmitted into a base band modulator 376 that, inturn, is connected to the PN spread/despread circuit 378 and an AFC loopphase detector 380. A frequency stable oscillator 382 works inconjunction with the numerically controlled oscillator 384 and the loopfilter 386. The frequency oscillators with sufficient frequencystability are coupled with carrier tracking loops with sufficientbandwidth to track out frequency and certainty caused by Dopplerfrequency ship as a result of two aircraft flying at maximum speeds inexcess of 500 m.p.h. in opposite directions.

In an attempt to maintain tighter control over aircraft departure andlanding times, some airlines require their flight crews to record Out,Off, On and In (OOOI) times by hand on a per flight basis. The flightcrew may verbally relay the "out" and "off" times after departure totheir ground based dispatch operations via a VHF transceiver. Thecaptain's clock in the flight deck is used as the time source.

In this type of prior art system, the "out" time is defined as themoment in time when the aircraft pushes back from the gate. The releaseof a parking brake usually signifies the "out" time. Once the enginesstart, the aircraft proceeds with the taxi operation until the aircraftreceives clearance from Air Traffic Control to take off. The air/groundrelay is monitored to detect the precise moment when the aircraft wheelsleave the runway. This time is recorded as the "off" time, i.e., weightoff wheels.

The present invention is advantageous because it can eliminate the needof flight crews to manually communicate "off" times. Because this timeis recorded and relayed during a high workload phase of flight, removingthis requirement from flight crews improves flight safety. From anoperating cost perspective, a significant amount of labor is eliminatedwith an automated process.

As noted before, the Ground Data Link (GDL) provides a wireless systemfor transferring data files to and from aircraft while on the ground atGDL equipped airports and can be used for reporting "OOOI" times.Further information concerning the reporting of "OOOI" times using theground data link can be found in U.S. Pat. Ser. No. 09/312,461, filedMay 14, 1999, entitled "System and Method of Providing OOOI Times of anAircraft," the disclosure which is hereby incorporated by reference inits entirety.

The system and method of the present invention also provides a wirelessmethod of transferring data files to and from aircraft while airborne inthe vicinity of GDL equipped airports. This system provides, in anon-limiting example, a means of automatically reporting "out" and "off"times from an aircraft in the vicinity of an airport, once the aircraftis airborne. This system also supports other applications, such asforwarding high priority aircraft performance diagnostic reports andflight crew messages.

The system and method of the present invention supports a flight safetyapplication, referred to as Flight Operational Quality Assurance (FOQA).As noted above, telemetry data is provided by hundreds of onboardaircraft sensors. This telemetry data is recorded during flight anddownloaded at GDL equipped airports. Flight files containing this dataare forwarded to the airline's flight safety department. Aircraft andflight crew performance is then assessed by flight safety analysts whoreview recorded flight files as part of the FAA's flight operationalquality assurance program. Corrective actions are identified andimplemented in maintenance operations and flight crew training asappropriate to improve flight safety.

Table I identifies FOQA and other envisioned applications that requirefiles to be downloaded from the aircraft after landing at a GDL equippedairport:

                  TABLE I                                                         ______________________________________                                                                        File Size                                     Application      File Type      (k Bytes)                                     ______________________________________                                        FOQA/Engine Maintenance                                                                        ARINC 717 Binary Data                                                                        3,390                                         Electronic Maintenance Logbook                                                                 ASCII Text     870                                           Cabin Maintenance Log                                                                          ASCII Text     20                                            OOOI "On" and "In" Times                                                                       ASCII Text     1                                             ______________________________________                                    

Table II identifies envisioned applications that require files to beuploaded to the aircraft prior to departure from a GDL equipped airport:

                  TABLE II                                                        ______________________________________                                                                      File Size                                       Application       File Type   (k Bytes)                                       ______________________________________                                        Flight Plan/Release                                                                             ASCII Text  10                                              Weight & Balance Report                                                                         ASClI Text  10                                              Graphical Weather GIF File    130                                             FMC Nav Data Base Updates                                                                       Binary File 1,000                                           Onboard Performance Computer                                                                    Executable File                                                                           10,000                                          Online Electronic Publications                                                                  HTML or Adobe                                                                             100                                             ______________________________________                                    

The system and method of the present invention also provides forcollision avoidance. Based on the manner in which the ATC manages enroute air transport aircraft flying along defined federal airways withdefined spacing, en route aircraft can periodically report their tailnumber and position as a function of latitude, longitude, and altitudeto aircraft within communication range. Each aircraft maintains thepositions of neighboring aircraft. The GDL system of the presentinvention provides access to telemetry data from aircraft flightperformance sensors. Thus, the en route data maintenance can be readilyimplemented. The GDL system of the present invention can also provide aninterface to a flight deck display, which could be used to graphicallydisplay the position of neighboring aircraft as a function of time inrelation to the aircraft under the control of the flight crew.

The ability to sustain communications once an aircraft is airborneenables the GDL system of the present invention to support airborne datamessaging applications that are currently supported via VHF radiocommunications over either ARINC or private airline voice and/or datanetworks. These systems suffer from various undesirable characteristicssuch as channel capacity limitations and a lack of voice privacy. Voicechannels are not only shared by all regional air traffic and grounddispatch or operations in a party line fashion, but conversations arerecorded by the FAA when ATC channels are utilized.

The advantages to an airline are considerable. These advantages includecapacity and low cost. In order to extend the communication range of theair-to-ground network, the data rate is reduced from about 11 Mbps toabout 355 Kbps. Naturally, this reduction is only exemplary, and theactual data rate will vary depending on technical and environmentallimitations, as known to those skilled in the art. This reduction indata rate improves the communication range of the network withoutadversely impacting its throughput. Further reductions in data rate arepossible. However, further data rate reductions could adversely impactthe cost of a transceiver and impact the actual data throughput andwould therefore have to be carefully considered by one skilled in theart. A resultant airborne data throughput at 355 Kbps is still almosttwo orders of magnitude greater than the 4.8 Kbps data throughputadvertised by most air-to-ground radiotelephone or SATCOM communicationchannels.

There are additional advantages that stem from being able to offer anair-to-ground link in conjunction with a ground-to-ground link. Addingan air-to-ground capability extends the amount of time available totransfer files to and from an aircraft while in the vicinity of theairport. An air-to-ground capability also helps lessen the impact ofground related multipath interference and blockage of signal qualitywhen the aircraft is parked at some gates.

In accordance with the present invention, the power and frequency of theGDL system of the present invention can be changed in order to complywith the regulatory requirements of the country where the GDLtransceiver is operating. Latitude and longitude information provided bylocation sensing devices is used to place the current location of thevehicle mounted transceiver within a predetermined set of geographicboundaries under the jurisdiction of government organizations chargedwith the management of RF frequency spectrum, e.g., the FederalCommunications Commission (FCC). Once the vehicle is known to be withina defined geographic area, the system automatically adjusts the transmitpower level and configures the frequency channel set, in order to assurecompliance with the rules of the governing regulatory body.

Recent advances in Global Positioning Satellite (GPS) receivertechnology have resulted in the widespread deployment of GPS receiversin a variety of communication vehicles, e.g., planes, trains andautomobiles. Modern aircraft are equipped with GPS receivers whichprovide latitude and longitude information to various aircraft avionicssystems. Older aircraft determine latitude and longitude based on otheronboard sensors, e.g., gyros, air speed and altitude, as well as onboardnavigation receivers and computers.

By way of background, GDL of the present invention can operate at 2.4GHz within the North American Industrial, Scientific and Medical (ISM)equipment frequency band allocated for unlicensed operation. Europe (ETS300 328) and Japan (RCR 27) also have frequency bands at 2.4 GHzdesignated for unlicensed operation. Most countries have allocatedportions of the 2.4-2.5 GHz band for unlicensed operation. The issuethis invention addresses is that the frequencies and maximum transmitpower levels vary from country to country. Table III illustrates theproblem:

                  TABLE III                                                       ______________________________________                                        Variation in Optimum Frequency Channels and Transmit                          Power Level as a Function of Country                                                                               Transmit                                 Country  Freq Ch A Freq Ch B Freq Ch C                                                                             Pwr                                      ______________________________________                                        US*      2427 MHZ  2457 MHZ  N/A      1 Watt                                  Canada*  2427 MHZ  2457 MHZ  N/A      1 Watt                                  Mexico*  2427 MHZ  2457 MHZ  N/A      1 Watt                                  New Zealand*                                                                           2427 MHZ  2457 MHZ  N/A      1 Watt                                  ETSI     2412 MHZ  2442 MHZ  2472 MHZ                                                                              100 mWatt                                (Europe)***                                                                   Germany***                                                                             2412 MHZ  2442 MHZ  2472 MHZ                                                                              100 mWatt                                Japan**  2484 MHZ  N/A       N/A     100 mWatt                                France*  2457 MHZ  N/A       N/A     100 mWatt                                Australia****                                                                          2411 MHZ  2439 MHZ  N/A     100 mWatt                                U.K.**   2460 MHZ  N/A       N/A     100 mWatt                                Spain**  2460 MHZ  N/A       N/A     100 mWatt                                ______________________________________                                         *Frequencies shown are the optimum choice for the GDL application. Others     are available but are less desirable.                                         **Frequency shown is the only frequency available.                            ***Only frequencies available if 3 simultaneous channels are required.        ****Only frequencies available if 2 simultaneous channels are required.  

The GDL system of the present invention uses location information tocontrol transmit power as opposed to information contained within aprobe message transmitted by a fixed, ground-based transmitter. Transmitpower is controlled to comply with local regulatory requirements asopposed to minimizing interference or power consumption.

The present invention uses location information to configure thefrequency channel set as opposed to signal quality estimates or somepseudo random algorithm. The frequency channel set is controlled tocomply with local regulatory requirements as opposed to maintaining oroptimizing link quality.

FIG. 5 illustrates the relative coverage areas, channel frequencyassignments, and data rates for a single "air" cell 20 represented byradio tower 24a and a single "ground" cell 22 represented by radio tower24 at an airport. The graph in FIG. 5A illustrates the frequencyspectrum.

In the system and method of the present invention, access to the overallnetwork is limited by regulatory body transmit power restrictions toproximal access to GDL equipped airports. Most airlines operate out ofhub airports to provide centralized locations for making connectionsbetween flights to and from remote stations. Because of any givenaircraft's frequency of visiting hub airports, they are preferredlocations for deploying GDL ground infrastructure of the presentinvention.

Because of the large concentration of aircraft in and out of these hubairports to allow passengers to make connections during specific windowsof time, these hub airports also offer the ability to significantlyextend their communication range to departing and arriving aircraft.Because air transport aircraft that fly in and out of busy airports haveATC managed separation distances, the aircraft are constrained to followdefined inbound and outbound vectors. These aircraft are furtherconstrained under IFR to follow defined Federal Airways, which onlyhelps to extend the communication range of the hub airport. These flightconstraints enable en route aircraft that are outside the communicationrange of the ground network to be used as wireless repeaters tosignificantly extend the range of the network, as shown in FIG. 6.

A variety of data messaging applications can occur immediately followingtakeoff and can be relayed or transmitted directly by the system andmethod of the present invention. One data messaging application providesthe actual "out" and "off" times for OOOI reporting. This capability canbe supported by this system either manually or automatically. Also,takeoff related engine events can be reported based on real timeparameter exceedances. Both of these applications are supported by theair-to-ground link.

FIG. 6A illustrates one cross-section of a jet engine indicatedgenerally at 400, showing basic components and engine air flow FADECcontrol 402 to and from the jet engine that can be used for real timemonitoring of engine events. These events could be downloaded during thefirst minute or so of initial take-off to a remote diagnostic centerthat could determine if on wing maintenance is warranted at thedestination station.

For purposes of clarity, reference numerals to describe this jet enginebegin in the 400 series. As shown in FIG. 6A, the engine air flow FADECcontrol 402 could include the core compartment bleeding; sumppressurization; sump venting; active clearance control; low pressure andhigh pressure recoup; and venting and draining functions. Thesefunctions could be monitored through basic FADEC control system 402, asknown to those skilled in the art. The engine example in FIG. 6Acorresponds to a General Electric CF6-80C2 advanced design with a FADECor PMC control having an N1 thrust management and common turbomachinery. Although this jet engine is illustrated, naturally othercontrol systems for different jet engines could be used, as known tothose skilled in the art.

The engine as illustrated has six variable stages and a ruggedized stageone blade with a low emission combuster and 30 pressurized nozzles andimproved emissions. It has a Kevlar containment to give a lowercontainment weight and a composite fan OGV. It has an enhanced HPT witha DS stage of one blade material and a TBC, with advanced cooling andactive clearance control.

The fan module includes an aluminum/Kevlar containment 404 and a 93-inchimproved aero/blade 406. It has compositive OGV's 408 with analuminum/composite aft fan case 410 and a titanium fan frame 412 forreduced losses. It additionally has a four stage orthogonal booster 414and a variable bypass valve (VBV) between the fan struts (with 12locations) 416. The engine includes a compressor inlet temperature (CIT)probe 418.

The high pressure compressor includes an IGV shroud seal 420 and a bladedovetail sealing 422 with a trenched casing of stages 3-14 424. Thecompressor includes a vane platform sealing 426 and a short cord stage 8low loss bleed system 428 and improved rubcoat reduced clearances 430.

The compressor rear frame includes a combuster 430 and ignitor plug 432with a fuel nozzle 434 and OGV 436. It includes a vent seal 438 and4R/A/O seal 440 and 4R bearing 442 and 4B bearing 444. It also includesa 5R bearing 446 and 5R/A/O seal 448, a diffuser 450 and pressurebalance seal 452. The compressor rear frame also includes a stage 1nozzle 454.

The high pressure turbine area includes an active clearance for controlstages 1 and 2, and coated shrouds indicated at 456. It also includesdirectionally solidified stage 1 blades and damped blades 458 and acooling air delivery system. The high pressure turbine include athermally matched support structure, and an active clearance control andsimplified impingement with a cradled vane support and linear ceiling.The improved inner structure load path has improved roundness control,solid shrouds and improved ceiling. These components are located in thearea generally at 460 of the high pressure turbine area.

Low pressure turbine technology area includes a clearance control 462, a360° case 464, aerodynamic struts 466 that remove swirl from the exitgas and a turbine rear frame 468 formed as a one piece casting.

Many of these components can have sensors and structural force sensorthat generate signals during initial take-off such that signals arerelayed via the ground data link unit to an on-ground maintenance crewand/or separate remote operations control center having its ownprocessor.

FIG. 6B illustrates components that were monitored during engine startin one example, including the engine hydraulic system, the oil pressure(psi), the engine cut-off switch, oil temperature (deg C), fuel flow(1b/hr), the N2L and N1L both in percentage terms, and oil temperatureand EGT, both in centigrade. The ranges are shown on the vertical axisof the graph, while time is shown on the horizontal axis of the graph.

This information can be downloaded via the ground data link unit of thepresent invention to a ground based processor, where a remote diagnosticcenter can determine if on wing maintenance is warranted at thedestination station.

Table II identifies two sets of possible post departure data messagingapplications:

                  TABLE IV                                                        ______________________________________                                                                    File Size                                         Application        File Type                                                                              (k Bytes)                                         ______________________________________                                        OOOI "out" and "off" times                                                                       ASCII text                                                                             1                                                 Engine event reporting                                                                           Binary file                                                                            0.3                                               ______________________________________                                    

Other post messaging applications, as will be described below, and otherapplications as suggested to those skilled in the art can also bedeveloped with the ground data link unit of the present invention. Thereare also en route data messaging applications that occur during approachthat also lend themselves to the GDL air-to-ground link of the presentinvention. Flight crews currently phone in their fuel weight so thatground operations can calculate how much fuel will need to be added forthe next flight. This allows more efficient scheduling and control overfuel resources. Also at this time, the aircraft crew receives their gateassignment from ground operations. En route wind and temperature datacould also be monitored during flight and automatically relayed todispatch prior to landing to aid in flight planning.

The Digital Automatic Terminal Information Service (ATIS) weatherinformation could be uploaded via an air-to-ground link. ATIS is thecontinuous broadcast of recorded non-control information in highactivity terminal areas. Its purpose is to improve pilot and controllereffectiveness and relieve frequency congestion by automating therepetitive transmission of essential but routine information. ATISinformation includes the latest hourly weather information, i.e.,ceiling, visibility, obstructions to visibility, temperature, dew point(if available), wind direction (magnetic) and velocity, altimeter, andin some instances, the instrument approach and the runway in use.

Table V identifies other approach data messaging applications that canbe used in the present invention:

                  TABLE V                                                         ______________________________________                                                                    File Size                                         Application        File Type                                                                              (k Bytes)                                         ______________________________________                                        Fuel weight reporting                                                                            ASCII text                                                                             1                                                 Gate assignment    ASCII text                                                                             1                                                 En route wind & temp reporting                                                                   ASCII text                                                                             10                                                Digital ATIS       ASCII text                                                                             10                                                ______________________________________                                    

Other applications can be used as noted before, and as suggested bythose skilled in the art. Other important features that can beincorporated into the ground data link of the present invention include:

1. The use of en route aircraft acting as repeaters to extend thecommunication range of the airport ground infrastructure.

2. Raising the above ground antenna height of the aircraft in order toeliminate ground multipath, the dominant propagation loss factor interrestrial radio communication links.

3. The reduction of link data rate and corresponding narrowing ofbaseband filters to improve signal-to-noise ratio and thereby increasecommunication range.

4. The selection of a frequency use band below the resonant frequency ofoxygen and water molecules in order to minimize the effects ofatmospheric absorption loss and rain fading on communication range.

5. The use of Omni-directional antennas 28 on the ground to provide gainfor both the airborne and ground based applications, such as shown inFIG. 7.

6. The use of frequency oscillators with sufficient frequency stabilitycoupled with carrier tracking loops with sufficient bandwidth to trackout frequency uncertainty caused by Doppler frequency shift as a resultof two aircraft flying at maximum speeds in excess of 500 miles/hour inopposite directions.

The following description will now proceed using as example a vehicle,e.g., aircraft. The ground data link unit of the present invention couldbe used on different moving vehicles besides an aircraft.

In one embodiment shown in FIG. 8, vehicle-based (e.g., aircraft based)communications processor 30 receives data from aircraft telemetrysensors for subsequent transmission to a ground-based Wide Area Network(WAN) 32 while the vehicle is en route, as will be explained. Thevehicle-based communications processor 30 formats the data for transportat the network and transport layer and sends the formatted data toWideband Spread Spectrum Transceiver 34, along with the address of thedestination node, which is part of the end node of a mobile transceiveracting as an interface to a vehicle information processor, as shown bydotted lines at 36.

The wideband spread spectrum transceiver 34 formats the data fortransmission at the data link layer and transmits the data via atransportation vehicle mounted antenna 38. The wideband spread spectrumtransceiver 34 transmits within a frequency band below the resonantfrequency of oxygen and water molecules in order to minimize the effectsof atmospheric absorption loss and rain fading on the communicationrange. The wideband spread spectrum transceiver 34 also uses a lowerdata rate than that used on the ground and correspondingly narrows itsbaseband filters to improve the signal-to-noise ratio and therebyincrease the communication range.

A transportation vehicle mounted antenna 40, which is part of a mobiletransceiver acting as a wireless repeater 42, is externally mounted on asecond transportation vehicle that is within the communication range ofboth the first transportation vehicle, and the ground-based WAN accesspoint, indicated by dotted line 44. The transportation vehicle mountedantenna 40, which is connected to a wideband spread spectrum transceiver46, receives the transmission from the transportation vehicle mountedantenna 38. The wideband spread spectrum transceiver 46 uses a frequencyoscillator with sufficient frequency stability and a carrier trackingloop with sufficient bandwidth to track out the frequency uncertaintycaused by any Doppler frequency shift.

The worst case Doppler shift occurs as a result of two aircraft flyingat maximum speeds in excess of 500 miles/hour in opposite directions.The wideband spread spectrum transceiver 46 recognizes the destinationaddress contained within the transmission as being associated with theground-based WAN access point with which it can also communicate. Thewideband spread spectrum transceiver 46 retransmits each data packetthat it receives from the wideband spread spectrum transceiver 34, viathe transportation vehicle mounted antenna 40. The wideband spreadspectrum transceiver 46 retransmits each data packet so that theground-based WAN access point 44 can receive each packet.

As further illustrated, an omni-directional ground antenna 48 at theaccess point 44 is connected to the wideband spread spectrum transceiver50, and receives a transmission from the transportation vehicle mountedantenna 40. The omni-directional ground antenna 48 is installed on amast atop a building or other structure in order to position it as highabove the ground as practical. Raising the above ground antenna heighthelps to eliminate ground multipath, the dominant propagation lossfactor in terrestrial radio communication links.

The omni-directional ground antenna 48 provides gain in an upwarddirection, in order to support air-to-ground communications as well asgain in a downward direction, in order to support ground-to-groundcommunications. The wideband spread spectrum transceiver 50 also employsa frequency oscillator with sufficient frequency stability and a carriertracking loop with sufficient bandwidth to track out the frequencyuncertainty caused by Doppler frequency shift. The wideband spreadspectrum transceiver 50 recognizes the destination address containedwithin the transmission as being associated with a ground-based WANnetwork device and forwards the data packets it receives to theground-based wide area network 32.

The air-to-ground link is advantageous as described and the followingresults give examples of its usefulness, taking into account factorssuch as Doppler and weather. In addition, given the landing anddeparture rates at airports where airlines have a large number ofallocated gates, air-to-air links are a viable means of extending anaircraft's access to the ground network in the vicinity of an airport.There are also routine airline applications that could benefit from thedescribed air-to-ground capability in the vicinity of major airports.

The communication range for a GDL air-to-ground link of the presentinvention can be about 21.6 miles (114,000 feet), as shown by theanalysis below:

    __________________________________________________________________________    To calculate Receive Power, Pr:                                               P = Pt(dBm) = Gr(dBi) + Gt(dBi) + Lambda\-- 2/(4sd)\-- 2(dB) + Lo             where dBi = dB's referenced to isotropic gain                                 Pt = Transmit power in dBm    Enter Pt:                                                                             30.00                                   Gt = Transmit antenna gain in dBi                                                                           Enter Gt:                                                                             0.00                                    Gr = Receive antenna gain in dBi                                                                            Enter Gr:                                                                             5.15                                    Lambda (wavelength) = 300/fc in MHZ                                                                         Enter fc:                                                                             2,462.00                                d = Distance in feet          Enter d:                                                                              114,150.00                              Lo = Other misc link losses in dB                                                                           Enter Lo:                                                                             (0.25)                                  Pr = Receive power in dBm     Answer Pr:                                                                            (96.2)                                  To calculate Path Loss, Ls:                                                   Ls = Pr(dBm) - Pt(dBm) - Gt(dBi) - Gr(dBi)                                    Where Ls = Path Loss in dB    Answer Ls:                                                                            (131.35)                                To calculate Receive Sensitivity, G/T°:                                G/T° = Gr(dBi) - Ts(dB)                                                Where F = Receive Noise Figure in dB                                                                        Enter F:                                                                              7.01                                    Tr = Effective Rx noise temp, °K                                                                     Answer Tr:                                                                            1,166.79                                Tr = Effective Rx noise temp, (dB-K)                                                                        Answer Tr:                                                                            30.67                                   T1 = Link noise temp, °K                                                                             Enter T1:                                                                             100.00                                  Tp = Antenna physical temp, ° C.                                                                     Enter Tp:                                                                             43.33                                   Ta = Antenna noise temp, °K                                                                          Answer Ta:                                                                            144.49                                  Ts = System noise temp, °K                                                                           Answer Ts:                                                                            1,311.29                                Ts = System noise temp, (dB-k)                                                                              Answer Ts:                                                                            31.18                                   G/T° = RX Sensitivity, Gr/Ts in dB-K                                                                 Answer G/T°                                                                    (26.03)                                 To calculate No and Pr/No:                                                    No = kT° (dBm/Hz)                                                      23)re K = Boltzmann's Constant (1,38*10\--                                    T° = Ts in degrees Kelvin                                              No = kT° in dBm/Hz     Answer No:                                                                            (167.42)                                Pr/No = Pr(dBm)-No(dBm)                                                       Where Pr/No = Received Pr/No in (dB-Hz)                                                                     Answer Pr/No:                                                                         71.22                                   To calculate Received Eb/No:                                                  Eb/No = Pr/No(dB-Hz) - R(db-bps) + Lo(dB)                                     Where R = Data bit rate in kHz                                                                              Enter R:                                                                              354.84                                  Lo = Implementation Loss im dB                                                                              Enter Lo:                                                                             (5.22)                                  Eb/No is in dBs               Answer Eb/No:                                                                         10.50                                   To calculate Link Margin, M:                                                  Where M = Received Eb/No(dB)-Required Eb/No(dB)                               Required Eb/No in dB, based on deniod                                                                       Enter Eb/No:                                                                          10.50                                   M = Margin in dB              Answer M:                                                                             (0.00)                                  __________________________________________________________________________

This calculated range is based on several assumptions. Some existing GDLground-to-ground link parameters have been assumed. An exception istransmit power, which has been increased to the full 1 watt allowed bythe FCC. A bottom mounted airborne antenna 40 is assumed with a 0 dBigain, based on a 3° elevation angle with respect to the ground antenna.Another exception is, of course, data rate, which has been reduced to355 kbps, as discussed previously. Along with the reduction in data ratecomes an additional 1.5 dB benefit in required Eb/No, due to theconversion from DQPSK to DBPSK modulation at the lower data rate. Anatmospheric absorption loss of 0.21 dB has been assumed, as discussedbelow regarding the Doppler.

Commercial Wireless LAN transceivers utilize inexpensive crystaloscillators that typically provide a frequency stability of 1-10 ppm.One type of GDL transceiver 136 used with the present invention has afrequency stability of ±12 kHz, which translates to ±5 ppm at 2400 MHZ.Thus, the frequency uncertainty between any two transceivers can be aslarge as 24 kHz. An analysis of the carrier tracking loop shows that thedesign can accommodate as much as 125 kHz of frequency uncertainty, withonly a 0.22 dB degradation in demodulator performance due to the symbolcorrelation error at a data rate of 2 Mbps. At 355 kbps, the design canaccommodate only 44 kHz of frequency uncertainty for the same 0.22 dBdegradation in S/N.

The frequency uncertainties can be calculated as follows. An I and Qcomplex demodulator convolves the internally generated PN sequence at astationary frequency with the input signal. Because non-coherent DPSKmodulation is used, the I and Q vector correlation output rotates duringa symbol time as a function of oscillator drift or Doppler on the inputsignal. The correlation vector angle therefore can change from the startof the symbol to the end of the symbol. The magnitude of the vectorfalls off about 0.22 dB at 45° rotation. Beyond 45° rotation, themagnitude of the vector drops rapidly and the symbol decision errorsincrease. 45° is therefore a reasonable limit of acceptability for thepurpose of this analysis. The amount of frequency offset, Δf, of theinput signal required to produce a 45° rotation is:

    Δf/1 Msps=45°/360°

    Δf=125 kHz

Solving the equation for Δf produces a result of 125 kHz for a symbolrate of 1 Msps (there are 2 bits/symbol for DQPSK). Solving this sameequation for a symbol rate of 355 ksps (1 bit/symbol for DBPSK) producesa result of 44 kHz as shown:

    Δf/355 ksps=45°/360°

    Δf=44 kHz

The Doppler frequency shift at 2465 MHZ that results from a B737-700flying at its maximum airspeed of 530 miles/hour with respect to a fixedground station is approximately 2 kHz. The frequency offset due toDoppler is defined by the following equation:

    Δf.sub.d =(ν/c)*f.sub.c

where

ν=relative velocity,

ν=(530 mi/hr) (1.61×10³ m/mi) (1 hr/60 min) (1 min/60 sec)=237 m/s

where

c=speed of light=3×10⁸ m/s

and where

f_(c) =2465 MHz

    Δf.sub.d (237 m/s)/(3×108 m/s)*2465 MHz=1.95 KHz

The total frequency uncertainty of two transceivers, each mounted on anaircraft flying at maximum speed in opposite directions is as follows:

    Δf=(Δf.sub.o +Δf.sub.d +Δf.sub.o +Δf.sub.d)

    Δf=(12kHz+2kHz+12kHz+2kHz)=28 kHz

The resulting 28 kHz of total frequency uncertainty is well within thepreviously defined limit of 44 kHz for a 355 kbps symbol rate.Therefore, the Doppler shift due to aircraft in flight has a negligibleeffect on system bit error rate.

The atmospheric absorption loss for a 2.4 GHz ISM Band due to water andoxygen molecule resonance is about 0.0115 dB/mile. This figure of meritis the basis for "other miscellaneous link losses" used to calculate thecommunication range in the previous section. During heavy rain, thepropagation loss for the 2.4 GHz ISM Band increases to nearly 0.5dB/mile. Weather is usually not a concern for terrestrial applications,because practical distances are normally constrained by multipathinterference to less than a mile. For airborne applications, however,where signal fading due to multipath is relatively nonexistent andcommunication range approaches that of free space, this loss needs to beaccounted for in the overall link budget analysis.

The communication range for a GDL air-to-ground link in heavy rain is11.5 miles (60,650 feet), as shown by the analysis below:

    __________________________________________________________________________    To calculate Receive Power, Pr:                                               P = Pt(dBm) = Gr(dBi) + Gt(dBi) + Lambda\-- 2/(4sd)\-- 2(dB) + Lo             where dBi = dB's referenced to isotropic gain                                 Pt = Transmit power in dBm    Enter Pt:                                                                             30.00                                   Gt = Transmit antenna gain in dBi                                                                           Enter Gt:                                                                             0.00                                    Gr = Receive antenna gain in dBi                                                                            Enter Gr:                                                                             5.15                                    Lambda (wavelength) = 300/fc in MHZ                                                                         Enter fc:                                                                             2,462.00                                d = Distance in feet          Enter d:                                                                              60,650.00                               Lo = Other misc link losses in dB                                                                           Enter Lo:                                                                             (5.74)                                  Pr = Receive power in dBm     Answer Pr:                                                                            (96.20)                                 To calculate Path Loss, Ls:                                                   Ls = Pr(dBm) - Pt(dBm) - Gt(dBi) - Gr(dBi)                                    Where Ls = Path Loss in dB    Answer Ls:                                                                            (131.35)                                To calculate Receive Sensitivity, G/T°:                                G/T° = Gr(dBi) - Ts(dB)                                                Where F = Receive Noise Figure in dB                                                                        Enter F:                                                                              7.01                                    Tr = Effective Rx noise temp, °K                                                                     Answer Tr:                                                                            1,166.79                                Tr = Effective Rx noise temp, (dB-K)                                                                        Answer Tr:                                                                            30.67                                   T1 = Link noise temp, °K                                                                             Enter T1:                                                                             100.00                                  Tp = Antenna physical temp, ° C.                                                                     Enter Tp:                                                                             43.33                                   Ta = Antenna noise temp, °K                                                                          Answer Ta:                                                                            144.49                                  Ts = System noise temp, °K                                                                           Answer Ts:                                                                            1,311.29                                Ts = System noise temp, (dB-k)                                                                              Answer Ts:                                                                            31.18                                   G/T° = RX Sensitivity, Gr/Ts in dB-K                                                                 Answer G/T°                                                                    (26.03)                                 To calculate No and Pr/No:                                                    No = kT° (dBm/Hz)                                                      23)re K = Boltzmann's Constant (1,38*10\--                                    T° = Ts in degrees Kelvin                                              No = kT° in dBm/Hz     Answer No:                                                                            (167.42)                                Pr/No = Pr(dBm)-No(dBm)                                                       Where Pr/No = Received Pr/No in (dB-Hz)                                                                     Answer Pr/No:                                                                         71.22                                   To calculate Received Eb/No:                                                  Eb/No = Pr/No(dB-Hz) - R(db-bps) + Lo(dB)                                     Where R = Data bit rate in kHz                                                                              Enter R:                                                                              354.84                                  Lo = Implementation Loss im dB                                                                              Enter Lo:                                                                             (5.22)                                  Eb/No is in dBs               Answer Eb/No:                                                                         10.50                                   To calculate Link Margin, M:                                                  Where M = Received Eb/No(dB)-Required Eb/No(dB)                               Required Eb/No in dB, based on deniod                                                                       Enter Eb/No:                                                                          10.50                                   M = Margin in dB              Answer M:                                                                             (0.00)                                  __________________________________________________________________________

With the present invention, it is possible to accommodate a greaternumber of planes at an airport. At a typical airport, an aircraft mayspend 20 minutes at a gate. For example, at one aircraft station with 27gates, the station can accommodate a peak influx of one aircraft every45 seconds. A higher influx rate would result in more aircraft on theground than the 27 gates could accommodate.

With the extended range GDL system of the present invention, it ispossible to accommodate a higher influx rate, up to one aircraft every30 seconds. This analysis clearly illustrates that the GDL system of thepresent invention provides sufficient bandwidth to accommodate the needsof different airlines. Furthermore, the GDL system of the presentinvention can be easily expanded to provide twice the capacity byincreasing the number of frequency channels used, if necessary.

Table VI shows the departure metrics for an example of 12 busy stations.Based on the assumption that a given aircraft's destination is trulyrandom, the table shows that the probability of having one of these 12stations as a destination is 54%. The table also shows the probabilitiesof hitting one of these 12 stations within one to eight trips. Theprobability of landing at one of these 12 stations within eight flightlegs is 99.8%. Given that the average number of flight legs per day is8.7, then a given aircraft would encounter a GDL equipped airport atleast once a day.

                                      TABLE VI                                    __________________________________________________________________________    Equipping an Airline's Busiest Stations Results in at Least                   One GDL Stop Per Day                                                          SWA   Airport                                                                           Number                                                                            Maintenance                                                                         Intermediate                                                                        Weekly                                                                             GDL GDL                                        Stations                                                                            Code                                                                              of Gates                                                                          Operations                                                                          Stations                                                                            Departures                                                                         Prionty                                                                           Departutes                                 __________________________________________________________________________    Phoenix                                                                             PHX 27  X           1122 1   1122                                       Las Vegas                                                                           LAS 12        X     957  2   957                                        Houston                                                                             IAH 11  X           939  3   939                                        Dallas                                                                              DAL 13  X           909  4   909                                        Los Angeles                                                                         LAX 9               785  5   785                                        Oakland                                                                             OAK 11        X     738  6   738                                        Chicago                                                                             MDW 19  X           690  7   690                                        Midway                                                                        St. Louis                                                                           STL 8         X     593  8   593                                        San Diego                                                                           SAN 7               527  9   527                                        San Jose                                                                            SJC 6               464  10  464                                        Baltimore                                                                           BWI 6         X     422  11  422                                        Nashville                                                                           BNA 5         X     409  12  409                                        Total                     15784                                                                              8555                                           Departures:                                                                   Probability of hitting a GDL Equipped Station in one trip                                                        54.20%                                     Probability of hitting a GDL Equipped Station once in 2                                                          79.02%                                     Probability of hitting a GDL Equipped Station once in 3                                                          90.39%                                     Probability of hitting a GDL Equipped Station once in 4                                                          95.60%                                     Probability of hitting a GDL Equipped Station once in 5                                                          97.98%                                     Probability of hitting a GDL Equipped Station once in 6                                                          99.08%                                     Probability of hitting a GDL Equipped Station once in 7                                                          99.58%                                     Probability of hitting a GDL Equipped Station once in 8                                                          99.81%                                     __________________________________________________________________________

The 30 second metric for the amount of time it takes to accomplish allfile transfers to and from an aircraft once it reaches the ground at oneof the proposed 12 GDL equipped stations is based on the followingassumptions. Six of the 12 GDL equipped stations have more than 10 gatesand six have fewer than 10 gates. The analysis assumes that the oncemonthly flight deck computer and FMC uploads take place at one of thesix GDL equipped stations having fewer than 10 gates. All other routinefile transfers are assumed to take place at any of the 12 GDL equippedstations. The supporting analysis is shown in the following Table VIIfor the airports with more than 10 gates, and Table VIII for theairports with fewer than 10 gates.

                                      TABLE VII                                   __________________________________________________________________________    Required Access to GDL Network per Aircraft at GDL                            Equipped Stations with More than 10 Gates                                                                        Air vs.                                    Description     Direction                                                                            Size (kB)                                                                           When  Gnd                                        __________________________________________________________________________    FDC Updates     Upload 10,000                                                                              Current                                                                             Gnd                                        FMC Uploads     Upload 1,000 Current                                                                             Gnd                                        Electronic Maintenance Logbook                                                                Download                                                                             870   Future                                                                              Gnd                                        FOQA/Engine Trend Data                                                                        Download                                                                             3,390 Current                                                                             Gnd                                        OOOI Time Reports                                                                             Download                                                                             1     Current                                                                             Gnd                                        Weight & Balance Reports                                                                      Upload 10    Future                                                                              Gnd                                        Flight Release  Upload 10    Future                                                                              Gnd                                        Cabin Maintenance Log                                                                         Download                                                                             20    Future                                                                              Gnd                                        Graphical Weather                                                                             Upload 130   Future                                                                              Gnd                                        Total                  4,431                                                  Time in minutes @ 1.2 Mbps                                                                           0.49  29,54202                                                                            seconds                                    Min rq'd RF Link Data Rate in Mbps                                                                   1.33                                                   Assumptions                                                                   Compression Ration                                                                            2.00                                                          RF Link Overhead                                                                              0.67                                                          Flights/Day Round (2300/264,1)                                                                8.7                                                           Flt-Hrs/Day/Aircraft (8.7*1.33)                                                               11.571                                                        Avg Flight Time (hrs)                                                                         1.33                                                          Time Between GDL Stops (days)                                                                 1                                                             No of Gates at Hub/Station                                                                    27                                                            Avg time on Ground at Gate (mins)                                                             20                                                            Peak Landing Rate (sec)                                                                       44.4444444                                                    __________________________________________________________________________

                                      TABLE VIII                                  __________________________________________________________________________    Required Access to GDL Network Per Aircraft At GDL                            Equipped Stations with Less than 10 Gates                                                                        Air vs.                                    Description     Direction                                                                            Size (kB)                                                                           When  Gnd                                        __________________________________________________________________________    FDC Updates     Upload 10,000                                                                              Current                                                                             Gnd                                        FMC Uploads     Upload 1,000 Current                                                                             Gnd                                        Electronic Maintenance Logbook                                                                Download                                                                             870   Future                                                                              Gnd                                        FOQA/Engine Trend Data                                                                        Download                                                                             3,390 Current                                                                             Gnd                                        OOOI Time Reports                                                                             Download                                                                             1     Current                                                                             Gnd                                        Weight & Balance Reports                                                                      Upload 10    Future                                                                              Gnd                                        Flight Release  Upload 10    Future                                                                              Gnd                                        Cabin Maintenance Log                                                                         Download                                                                             20    Future                                                                              Gnd                                        Graphical Weather                                                                             Upload 130   Future                                                                              Gnd                                        Total                  15,431                                                 Time in minutes @ 1.2 Mbps                                                                           1.71                                                   Min rq'd RF Link Data Rate in Mbps                                                                   1.55                                                   Assumptions                                                                   Compression Ration                                                                            2.00                                                          RF Link Overhead                                                                              0.67                                                          Flights/Day Round (2300/264,1)                                                                8.7                                                           Flt-Hrs/Day/Aircraft (8.7*1.33)                                                               11.571                                                        Avg Flight Time (hrs)                                                                         1.33                                                          Time Between GDL Stops (days)                                                                 1                                                             No of Gates at Hub/Station                                                                    9                                                             Avg time on Ground at Gate (mins)                                                             20                                                            Peak Landing Rate (sec)                                                                       133.333333                                                    Engine Trend Data (kB/Flt-br)                                                                 586                                                           FDC, FMC Updates not included at stations with < 10 gates                     __________________________________________________________________________

Table IX shows one basis for estimating the size of the combinedFOQA/Engine Trend Data Files. The number of 12 bit words and some samplerates are based on the B757-200 FOQA files that are currently downloadedfor one known airline. In this example, these files are approximately345,600 bytes in size per flight hour. The contained parameters aresampled once every second, once every two seconds, once every fourseconds, and once every 64 seconds. The file size increases fromprevious files because some parameters are sampled as often as fourtimes/second for 15 minutes of every one hour flight. Some parametersare sampled as often as once per second instead of one every two or fourseconds for the duration of the flight.

                                      TABLE IX                                    __________________________________________________________________________    Basis for Estimating FOQA/Engine                                              Trend Data File Size                                                          Estimated FOQA/Engine Trend Data Fite Size                                           Number                                                                        of        Flight    Flight                                             Parameter                                                                            12 Bit                                                                             Sample                                                                             Duration                                                                           Sample                                                                             Duration                                                                             File                                        Type   Words                                                                              Rate (Hz)                                                                          (mins)                                                                             Rate (Hz)                                                                          (mins) Size                                        __________________________________________________________________________    Miscellaneous,                                                                       32   O.015625                                                                           15   0.015625                                                                           45      2700                                       Noncritical                                                                   Startup,                                                                             20   4    15   1    45     189000                                      Takeoff,                                                                      Shutdown                                                                      Flight Duration                                                                      20   1    15   1    45     108000                                      Critical                                                                      Miscellaneous,                                                                       53   1    15   1    45     286200                                      Critical                                                                      __________________________________________________________________________

FIG. 9 illustrates one possible airline network architecture in oneembodiment of the present invention. The entire network is based on theubiquitous, Internet standard TCP/IP protocols. A future TCP/IP toTP4/CLNP gateway is shown for compatibility with the current industrybaseline for ATC networking. For purposes of clarity, reference numeralsdescribing this aspect of the present invention will being in the 500series.

FIG. 9 illustrates this efficient system showing the aircraft system bydashed line indicated at 500, a GDL airport terminal indicated by dashedline at 502, and the dispatch, flight operations indicated by dashedline at 504. These three units connect into the public switchedtelephone network and airline wide area network 506, which includesrepresentative public switches. The aircraft system includes a GDL unit510 positioned on an aircraft that connects via a data connection 512 tothe GDL airport terminal 502 with a bridge 514 and a gateway 516 to SunSPARC computer terminal 518 as a representative processor. The GDLairborne unit also connects to an Ethernet backbone 520 that can connectvia a wireless link 522 to a flight deck computer 524, an ASCII printeras part of a flight deck printer 526, and a cabin PC 528. The GDLairborne unit 510 can also connect to the FDAM/DFDAU/DMU 530 and a cabintelecommunications unit (CTU), i.e., telephone switch, 532 outside thesystem. The telephone switch can connect voice and data through a part22.801 air-ground radio telephone or other cellular service to anair-ground radio tower 534 and a radio net 538 through an Iridium orother satellite service provider 538. Voice only communication can beestablished via a VHF comm transceiver 540 through the airline's privateradio network. At the dispatch flight operations 504, dispatch telephone542 can connect through the airline's PBX/PABX 548 to router and gateway544, 546 as known to those skilled in the art. These components connectto various terminals 550, which could include IBM or Sun SPARC workstations as known to those skilled in the art. Additionally, for engineevent reporting, data relating to engine events can be reported directlyto an engine trending area having a gateway 554 and Sun workstations556.

As noted above, the ground data link network of the present inventioncan use standard TCP/IP network protocols along with Ethernet data linkprotocols to provide computer communications among the GDL networkedhost. The TCP/IP protocol incorporates Internet networking, allowinghost peer-to-peer connectivity. The GDL network implements thistechnology into a private network as illustrated in FIG. 9 for GDL hostcommunications. The example of the merging of an airline network and GDLnetwork is now described with reference once again to FIG. 9.

The GDL Wide Area Network (WAN) hardware architecture could includemultiple airport terminal local area networks (LANs) and a singleAirline Operational Control Center (AOCC) LAN. Components within eachLAN include multiple host nodes (such as the illustrated Sunworkstations, PCs, wireless access nodes) and a network gateway. EachLAN could provide a 10 or 100 megabit Ethernet connection to implementthe data link protocol, as is well known to those skilled in the art.Each host attachment to the LAN could be accomplished via an Ethernetbased network interface card (NIC). Each LAN could include an ISDNgateway attachment for inter-LAN communication, providing 64 kbit to 256kbit data transmissions.

Each GDL network host would typically have Commercial Off The Shelf(COTS) software installed providing network connectivity control. Thiswould include Ethernet drivers for the NICs and a TCP/IP network kernelimplementing transport and Internet TCP/IP network layer protocols. Eachhost includes TCP/IP application protocols to implement common networkoperations. In addition, various TCP/IP network server applicationscould be installed on Sun workstations to support typical networkingoperations (ex. FTP, Email, NFS).

The GDL network could be pre-configured as a private TCP/IP network.Each LAN in the network could be identified as a subnet domain andassigned a unique subnet identified IP address. Each network componentattached to a subnet could be assigned a unique IP address for thatparticular domain. This would be a static IP address assignment andwould not be altered after installation. A domain name server would notbe employed on the GDL network, and therefore, each host would containinternal IP address information of other GDL host for networkconnectivity. Each networked host would be an identification tablecontaining available host names matched with assigned IP addresses. Thehost network applications would use either an IP address or host name toidentify and communication with another host on the network.

The GDL IP address is a 32-bit "class A" IP address, and is used forprivate network operation (10.0.0.0 domain). In this describedembodiment, this IP address format consists of four fields: class,network identifier, subnet identifier, and host identifier. Table Xdescribes the GDL IP address format using the TCP/IP standard withsubnetting for the GDL network.

                  TABLE X                                                         ______________________________________                                        Class A - IP Address Format                                                           Network           SubNet      Host                                    Class   ID                ID          ID                                      0       1      7          8   15      16  31                                  Fieldname Bit Position    Purpose                                             ______________________________________                                        Class     0               Class A IP format                                   Network ID                                                                              1-7             Private Network ID                                  SubNet ID  8-15           Subnet ID                                           Host ID   16-31           Individual host ID                                  ______________________________________                                    

In order to integrate the GDL and another computer network, an organizedplan for the resultant network architecture is developed. Typically, anairline network uses TCP/IP network protocol over an Ethernet data linkbackbone. Naturally, there may be areas of incompatibility that wouldhave to be resolved for this integration effort. The GDL networkarchitecture has the flexibility for modifications to conform with otherTCP/IP based networks. When the integration effort is complete, therevised representative airline and GDL network would be viewed as asingle operational computer network, rather than two distinctinterconnected networks.

Some airline networks are formed as a private WAN network utilizingTCP/IP for the network protocol along with a 10 megabit Ethernet tosupport the network data link. Because both airline and GDL networksincorporate Ethernet to provide the data link network functionality,this networking area should be compatible. Cabling for the GDL networktypically uses 10Base-T for physical connectivity requirements, however,it is adaptable to other existing Ethernet cabling standards.

For inter-networking activities, GDL utilizes ISDN gateways to providenetwork connectivity. However, GDL is not limited to ISDN and canincorporate other existing gateway components utilized by therepresentative airline.

Since both the airline and GDL network hosts include a TCP/IP networkkernel and Ethernet drivers, the basic network software control for eachnetwork component should be in place. In addition, any serverfunctionality to be shared between the networks needs examination toensure proper operation. Also there may be a merging of some softwareprocess currently used on both networks into a single networkapplication (e.g., Email server). This requires verification of theassociated network operation within the integrated network structure.

Each host on the airline and GDL network employs a TCP/IP network kernelto implement networking activities. However, the capability of thenetwork configuration between these two systems requires additionalconsideration. The TCP/IP standard requires a unique 32-bit IP addressassignment to identify each individual network host.

The format of the GDL IP address is configured to incorporate subnetaddressing. This addressing scheme provides a three-level hierarchy ofidentification: network, subnet and host identification. This subnettingimplementation allows for multiple network domains within the GDL globalnetwork structure. Each GDL airport terminal system is assigned aparticular subnet domain and all network hosts within that domain areassigned IP addresses using the subnet identification. Integration ofthe airline network and GDL network will require a review of the IPaddress format used within each network. Assuming the airline networkutilizes network domains and there exist available IP addresses, the GDLnetwork would adapt the airline address format.

For host network identification, each host on the GDL network has beenpre-assigned a unique IP address. This is a static address and will notchange following installation. However, should the airline networkrequire the use of a dynamic IP address assignment (e.g., dynamic hostconfiguration protocol), the present GDL network component IP addressallocation scheme can be reconfigured to obtain its IP address from theairline IP address allocation network server.

To connect to a computer on the GDL network, each GDL host has aninternal table, containing IP addresses and associated computer names,and listing all other available hosts on the network. Whenever acomputer name is selected for connection, the address table is utilizedto determine the associated host IP address. However, should the airlineemploy a domain name structure and utilize a Domain Name Server (DNS)for IP address lookup, the GDL host can be reconfigured to make use ofsuch a server to supply host addresses for network connectivity.

There are also two fundamental issues to be addressed when implementinga representative airline network architecture, which are a departurefrom traditional networks. The first is how to address the mobileaircraft LANs that roam from subnet to subnet. The second is, givenmultiple network connection options and associated costs, how to routefiles via the most economical path, while taking into considerationmessage priorities. The solution to the latter issue is illustrated inthe flow chart shown in FIG. 10.

The cost based routing algorithm shown in FIG. 10 is implemented in theGDL airborne segment, for files originating onboard the aircraft and inthe system controller located at the airline operational control center,for files originating from the ground network.

As shown in the flow chart of FIG. 10, when the IP datagram is received(Block 600), a determination is made whether the GDL path is available(Block 602). If it is, then the datagram is sent via the ground datalink unit (Block 604). If it is not available, then a determination ismade whether the file transfer has priority (Block 606). If thatdetermination is high, it is sent via the ATG phone (Block 608). If itis not, then a file transfer is delayed until a ground data link path isavailable (Block 610).

The proposed method for addressing the mobile aircraft LANs is anextension of the method GDL currently addresses the issue. When anaircraft lands at a GDL equipped airport, an IP address is dynamicallyassigned to it by a DHCP server application hosted on the sun SPARCserver shown in the GDL airport terminal equipment rack in FIG. 9. EachGDL equipped airport is a different subnet on the WAN. The temporaryDHCP IP address is, in effect, an alias that the GDL airborne segmentuses to transfer files over the TCP/IP based network. A systemcontroller (SC) at an airline operational control center recognizes theGDL airborne segment by its tray number, which is a hard coded series ofpins at an ARINC 600 connector interface. The system controllermaintains a database relationship between tray numbers and aircraft tailnumbers.

The GDL airborne segment is an end node or "client" on the network. Itcan also be a router for other clients on the aircraft LAN. To addressthis difference, it is possible to use a mobile IP, which is anextension to IP, and a recent Internet standard specified in RFC 2002. Amobile IP consists of three components: mobile nodes, foreign agents anda home agent. A system controller at an airline operational controlcenter is the home agent.

The GDL airborne segment (AS) acts as a foreign agent for the othermobile nodes connected to it on the aircraft LAN, as well as its ownforeign agent. When the AS comes up, it attempts to register with a GDLwireless router. If it is successful, it recognizes that it has proximalaccess to a GDL equipped airport and requests a temporary IP addressfrom the DHCP server. It then registers this "care of" address with thehome agent, i.e., the SC, and acts as its own foreign agent. It thensends out a "foreign" broadcast message to the other aircraft clients,and acts as their foreign agent as well. When the AS leaves the GDLequipped airport and can no longer receive a probe signal, it dials upthe SC via the ATG phone system, informs the home agent of its presenceon the home network, and defaults to its home network fixed IP address.Once the AS registers its home IP with the home agent, unless it hashigh priority files to transfer, it terminates the call to avoid usagefees. If the AS is on its home network, IP addressing and datagramdelivery to and from the AS, work as they would without mobile IP. Apossible mobile IP approach is illustrated in FIGS. 11A and 11B.

As shown clearly in FIG. 11A, the mobile node (OPC) 700 communicateswith the mobile node/foreign agent 702 of the ground data link airbornesystem (AS). This in turn can communication with the ATG phone system704. The system controller 706 acts as a home agent. FIG. 11Billustrates an example of the GDL airborne system acting as its ownforeign agent on a foreign subnet and a foreign agent for other mobilenodes. Instead of an ATG phone system radio tower, an airport terminalequipment rack 708. Steps are similar as in those steps of FIG. 11Aexcept between the mobile node/foreign agent 702 and the airportterminal equipment rack 708 acting as a PHX station.

From the perspective of the aircraft LAN mobile nodes, they aretypically on a foreign subnet and use the mobile IP provided to themfrom the AS acting as a foreign agent. The AS sends out a "foreign"broadcast message to the other aircraft mobile nodes and its current IP,depending on whether its connection options are the ATG phone system orGDL, respectively. If the GDL connection option is available, then theAS sends out its temporary DHCP IP address, or "foreign" address, whichthe aircraft LAN mobile nodes register with the home agent as their"care of" address. If the GDL connection option is not available, thenthe AS sends out its fixed IP address, or "home" address, which theaircraft LAN mobile nodes register with the home agent as their "careof" address.

Once the mobile nodes have registered with the home agent, all IPtraffic addressed to them is received by the home agent, encapsulated inanother IP datagram, and then "tunneled" to the foreign agent. Theforeign agent forwards the datagrams to their respective mobile nodes.In the reverse direction, the mobile nodes can bypass the home agent andsend datagrams directly to their destination.

Table XI provides an example of how the GDL system controller will keeptrack of available data communication options so that ground originatingnetwork traffic can be routed to the aircraft in the most cost effectivemanner possible. The table shows that the system controller identifiesthe phone number associated with each individual aircraft and either itsstatic, or "home" IP address, or its temporary DHCP "foreign" IPaddress. The process described in the preceding paragraphs guaranteesthat the lowest cost routing option is used for high priority messages,since the AS always registers its temporary DHCP "foreign" IP address ifit has proximal access to a GDL equipped airport. For low priority filetransfers, the AS and SC store the files until the GDL connection optionis available.

                  TABLE XI                                                        ______________________________________                                        Dynamic Messaging Address Table                                               Tail  Tray     Static Phone                                                                              AS Static                                                                              AS Dynamic                                Number                                                                              Number   Number      "Home" IP                                                                              "Foreign" IP                              ______________________________________                                        N631  xxxxxx   xxx.xxx.xxxx                                                                              xx.x.xxx.xx                                                                            xx.x.xxx.xx                               N632  xxxxxx   xxx.xxx.xxxx                                                                              xx.x.xxx.xx                                                                            xx.x.xxx.xx                               ______________________________________                                    

The following list describes the process steps that result in updatingthe dynamic IP address of a GDL accessible aircraft:

1. N631 lands at a GDL equipped station.

2. N631 registers with the network and is assigned a dynamic IP address.

3. N631 registers its temporary "foreign" IP and its tray number(xxxxxx) with the home agent, i.e., SC.

4. SC maintains the dynamic messaging address table.

5. SC uses the temporary "foreign" IP, when available, for all filetransfers.

6. N631 leaves the GDL equipped station and can no longer receive theABS probe.

7. N631 registers its "home" IP address with the home agent, i.e., SC.

8. SC replaces the temporary "foreign" IP with the "home" IP.

9. ABS returns surrendered IP address to DHCP pool.

10. SC always knows what data messaging connection options areavailable.

11. SC utilizes dynamic IP for all low priority and in-range highpriority messaging.

12. SC utilizes static IP for high priority messaging when aircraft isnot GDL accessible.

13. SC utilizes ubiquitous TCP/IP protocol stack for all file transfers,independent of connection method.

It is also possible to use the ground data link unit of the presentinvention to automatically distribute various updates of flightmanagement computer navigation database files for the air transportindustry. These updated files can have customized performance factors ona per aircraft basis.

As known, the air transport industry is required by the InternationalCivic Aviation Organization (ICAO) to update its navigation databasefiles every 28 days. As a result, air carriers typically purchase thesefiles from a company like Jeppesen, a leader in the navigation dataservices industry. Jeppesen offers a NavData Direct Update Service whichconverts the navigation database from the standard ARINC 424 specifiedformat to an airline's vendor specific avionics system. Using computersoftware developed by the avionics manufacturer and licensed toJeppesen, ARINC 424 data is formatted into customized updates that canthen be loaded directly into the airline's specific navigationequipment. A common media used to transfer this information is the IBMPC compatible 3.5" high density floppy disk.

Airlines receive, copy and disseminate navigation database files toevery aircraft in their fleet every 28 days. A programmable data loaderdevice is used to copy the files from the floppy disk to the aircraft'sflight management computer (FMC) 160 (FIG. 15). Typically each aircraftcontains one or two FMCs and either one or two interface connectorslocated in the flight deck. When the FMC is reprogrammed with a newnavigation database, customized performance factors such as drag factorand fuel flow are reset to the default values contained on thenavigation database media. If the performance factors for a givenaircraft should be different than the default values, then theseaircraft specific performance factors are recorded before the newnavigation database is loaded. Once the new navigation database isloaded, these default performance factors must then be manuallyreprogrammed back to their original value.

The programmable data loader receives its power from the FMC databaseloader interface connector. Once the programmable data loader powers upand passes its internal self test, status is displayed indicating thatthe unit is ready for operation and the floppy is inserted into the diskdrive. The file transfer begins automatically. Status is displayed onthe programmable data loader that indicates whether or not the datatransfer is in progress or complete. If the files reside on more thanone floppy, a disk change status is indicated to alert the user to swapdisks. If the data transfer fails, power is cycled to reset the dataloader and the process starts over.

Following the navigation database update, a series of manual processsteps are followed to verify that the FMC was programmed correctly.Because the FMC is designated as "flight critical," it is important toverify that it has been programmed correctly. The IDENT page on the CDUis checked to verify that the new NAV DATA has been loaded. The type ofaircraft and the type of engines are verified to reflect the correctaircraft configuration. The OP PROGRAM part number and the NAV DATA partnumber are verified against the proper part numbers obtained from theairline's technical operation's department. Today's date is verified tobe within the validity start and end dates of the navigation databasethat was loaded. If the default performance factors are used, then thedrag factor and fuel flow factors are also verified to be correct.

Once the first FMC is programmed, the process is either repeated for thesecond FMC using the data loader, or the files are copied from the firstFMC to the second FMC, depending on the aircraft and the availability ofa second interface connector. Once both FMCs have been programmed withthe new navigation database, any custom performance factors that need tobe changed from their default values are manually reprogrammed. One ofthe functions of the FMC is to provide an energy management function tooptimize flight performance based on cost, time, fuel or range. Theenergy management function is tailored to an individual airline'soperating economics, local fuel costs and the constraints of the airtraffic environment. Performance factors tend to be grouped as afunction of every airframe/engine combination. Drag factor, fuel flow,maneuver margin, approach speeds, optimum altitude, maximum altitude,minimum cruise time, minimum rate of change of climb, and minimum rateof change of cruise, are examples of performance factors that may becustomized to a value that is different from the default values. Theseperformance factors are manually programmed via the control/display unit(CDU) and are stored in the FMC's non-volatile memory. These performancefactors are typically changed in both FMCs at the same time, followingthe navigation database update.

These performance factors can be considered as falling into twocategories: static and dynamic. Drag factor is an example of a staticperformance factor that does not change from month to month unless theaircraft is physically modified. Cost index is an example of a dynamicperformance factor that can change on a per flight basis. If the flightis late in departing and the airline wishes to make up time, the costindex can be set to a lower value. This permits the aircraft to fly at alower than optimum cruise altitude and change altitude as a faster rate.This is less fuel efficient and therefore increases operating cost. Ifthe flight is on schedule, the cost index can be set to a higher value.This constrains the aircraft to change altitude at a slower rate and flyat a higher, more fuel efficient cruise altitude. This reduces operatingcost.

The logistics involved in planning, tracking and accomplishing the taskof updating each aircraft's flight management computer every 28 days isa formidable task. Most airlines have a great deal of diversity in theiraircraft fleet, in terms of airframe manufacturers, e.g., Boeing,McDonnell Douglas, Lockheed, Airbus, etc., families, e.g., B737, B757,B767, models, e.g., B757-300, B737-500, B737-700, etc. This translatesto dozens of airframe/engine combinations in hundreds of aircraft thatare spread over thousands of miles and are constantly in motion andsubject to highly dynamic scheduling changes. Sufficient copies ofrequired floppy disks are obtained and deployed along with programmableloader devices so that these new uploads can take place monthly atnumerous sites within minimum disruption to airline operations. The airtransport industry's entire process of disseminating, programming,verifying and customizing the navigation database is essentially amanual operation.

To further complicate the process, the FMC is not the only avionicsequipment that requires periodic software updates. Dozens of otherequipment require periodic updates and the list is growing in newerproduction aircraft. Just getting the right disks to the right aircraftat the right time requires significant effort and resources.

Generic airframe/engine based navigation database files can becustomized on a tail number unique basis. New navigation database filesfor each airframe/engine combination in an airlines' fleet are obtainedevery 28 days from a service such as Jeppesen's NavData Direct UpdateService. In a preferred embodiment, these files are obtained directlyfrom a secure Jeppesen web site via an Internet connection over thePublic Switched Telephone Network (PSTN). A variety of security featuresare implemented to authenticate the source files and ensure theintegrity of the file transfer process. These files are downloaded to adirectory on the GDL system controller. The performance factors for eachaircraft in the airlines' fleet is maintained in a database resident onthe GDL system controller on a per tail number basis. This database isaccessed by a software application which customizes the Jeppesenprovided navigation database files based on the unique performancefactors for each aircraft. This software application creates a uniqueset of navigation database files for each tail number in the fleetinventory.

The present invention also provides a system for automaticallydelivering new navigation database files to the aircraft. These tailnumber unique navigation database files are disseminated via the PSTN toaircraft specific directories resident on airport base station serverscontained within airport terminal equipment racks installed atGDL-equipped airports.

When aircraft land at GDL-equipped airports, the GDL airborne segmentinstalled on each aircraft connects to the airport base station servervia a wireless LAN connection. The GDL airborne segment moves the newnavigation database files from the tail number unique directory on theairport base station server to a directory resident within the GDLairborne segment.

The present invention also provides a method for reprogramming the FMCwith the new navigation database files. Once the new navigation databasefiles have been retrieved, the FMC is reprogrammed via the programmabledata loader interface. The GDL airborne segment is wired in parallel tothe programmable data loader interface connector located in the flightdeck. When power is removed from the GDL airborne unit, a high impedanceis presented to the FMC interface in order to preserve the existingmethod for reprogramming the FMC using a programmable data loader. ThisGDL airborne unit interface design is such that the GDL airborne unit isonly electrically connected to the FMC when the GDL airborne unit hasreceived new navigation database files, the aircraft is on the ground,and the GDL airborne unit is powered on. When these conditions are met,the GDL airborne unit reprograms the FMC with the new tail number uniquenavigation database files. The GDL airborne unit interface is alsodesigned so that failures cannot affect FMC performance.

This invention automates the following process steps:

1. Customizing the default performance factors in advance for eachindividual aircraft.

2. Delivering the new navigation database files to the aircraft.

3. Programming the FMC with the new navigation database files.

The fourth step is verifying that the FMC was programmed correctly. In asense, this step is accomplished automatically via the file transferprotocol and acknowledgment process defined in the ARINC 603 or ARINC615 airborne computer data loader specification. Based on the flightcritical nature of the FMC, the inventors do not imply that this stepcompletely eliminates the need to manually verify that the FMC wasprogrammed correctly once the new navigation database has bee loaded.

This application is related to copending patent applications entitled,"WIRELESS SPREAD SPECTRUM GROUND LINK-BASED AIRCRAFT DATA COMMUNICATIONSYSTEM WITH VARIABLE DATA RATE," "WIRELESS SPREAD SPECTRUM GROUNDLINK-BASED AIRCRAFT DATA COMMUNICATION SYSTEM FOR ENGINE EVENTREPORTING," "WIRELESS SPREAD SPECTRUM GROUND LINK-BASED AIRCRAFT DATACOMMUNICATION SYSTEM WITH APPROACH DATA MESSAGING DOWNLOAD," "WIRELESSSPREAD SPECTRUM GROUND LINK-BASED AIRCRAFT DATA COMMUNICATION SYSTEMWITH AIRBORNE AIRLINE PACKET COMMUNICATIONS," and "WIRELESS SPREADSPECTRUM GROUND LINK-BASED AIRCRAFT DATA COMMUNICATION SYSTEM FORUPDATING FLIGHT MANAGEMENT FILES," which are filed on the same date andby the same assignee, the disclosures which are hereby incorporated byreference.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is to be understood that the invention is not to belimited to the specific embodiments disclosed, and that themodifications and embodiments are intended to be included within thescope of the dependent claims.

That which is claimed is:
 1. A system for providing a retrievable recordof the flight performance of an aircraft comprising:a ground data linkunit that obtains flight performance data representative of aircraftflight performance during flight of the aircraft, said ground data linkunit comprising:a) an archival data store operative to accumulate andstore flight performance data during flight of the aircraft, and b) aspread spectrum transceiver coupled to said archival data store, andcomprising a transmitter that is operative after the aircraft completesits flight and lands at an airport to download said flight performancedata that has been accumulated and stored by said archival data storeduring flight over one of a plurality of sub-band frequency channels ofa spread spectrum communication signal, wherein said sub-band frequencychannel is chosen based on a position of the aircraft determined by anon board global positioning system in order to comply with anyregulatory frequency requirements of the geographical area in which theaircraft has landed; and an airport based spread spectrum receiver thatreceives the spread spectrum communication signal from the aircraft anddemodulates the signal to obtain the flight performance data.
 2. Asystem according to claim 1, wherein said ground data link unit furthercomprises an adaptive power control unit that varies the emitted powerlevel of the spread spectrum communication signal based on the positiondetermined by the on board global positioning system in order to complywith any regulatory power requirements of the geographical area in whichthe aircraft has landed.
 3. A system according to claim 2, wherein saidground data link unit further comprises a controller and memory having arecord of a plurality of geographical area and an emitted power level tobe used in each respective geographical area.
 4. A system according toclaim 1, wherein said ground data link unit further comprises acontroller and memory file having a record of a plurality ofgeographical areas and a respective sub-band frequency channel to beused in each respective geographical area.
 5. A system according toclaim 1, and further comprising an airport based archival data storecoupled to said airport based spread spectrum receiver that receives andstores said flight performance data.
 6. A system according to claim 5,and further comprising a wireless router that couples said airport basedspread spectrum receiver to said airport based archival data store.
 7. Asystem according to claim 1, and further comprising an airport basedserver coupled to said airport based spread spectrum receiver forreceiving flight performance data from the airport based spread spectrumreceiver.
 8. A system according to claim 1, and further comprising aremote flight operations center operatively coupled to said airportbased server for receiving and processing the retrieved flightperformance data.
 9. A system according to claim 1, wherein the spreadspectrum communication signal comprises a direct sequence spreadspectrum signal.
 10. A system according to claim 1, wherein the spreadspectrum communication signal comprises a signal within the S band. 11.A system according to claim 1, wherein the spread spectrum communicationsignal comprises a signal within the range of about 2.4 to about 2.5GHZ.
 12. A system according to claim 1, wherein said archival data storeof said ground data link unit further comprises means for compressingsaid flight performance data during the flight of the aircraft.
 13. Asystem for providing a retrievable record of the flight performance ofan aircraft comprising:a plurality of sensors located throughout theaircraft for sensing routine aircraft conditions and generatingparametric data such as received by a flight data recorderrepresentative of the aircraft flight performance during flight of theaircraft; a global positioning system on board the aircraft forgenerating position data reflective of the latitude and longitude of theaircraft; a multiplexer connected to the plurality of sensors and globalpositioning system for receiving the parametric data and position dataand multiplexing the parametric data and position data determined by theglobal positioning system; a ground data link unit connected to saidmultiplexer for receiving and multiplexing a sample of the multiplexedstream of parametric data and position data determined by the globalpositioning system, said ground data link unit comprising:a) an archivaldata store operative to accumulate and store flight performance dataduring flight of the aircraft, and b) a spread spectrum transceivercoupled to said archival data store, and comprising a transmitter thatis operative after the aircraft completes its flight and lands at anairport to download said flight performance data that has beenaccumulated and stored by said archival data store during flight overone of a plurality of sub-band frequency channels of a spread spectrumcommunication signal, wherein said sub-band frequency channel is chosenbased on a position of the aircraft determined by the on board globalpositioning system in order to comply with any regulatory frequencyrequirements of the geographical area in which the aircraft has landed;and an airport based spread spectrum receiver that receives the spreadspectrum communication signal from the aircraft and demodulates thesignal to obtain the flight performance data.
 14. A system according toclaim 13, wherein said ground data link unit further comprises anadaptive power control unit that varies the emitted power level of thespread spectrum communication signal based on the position determined bythe on board global positioning system in order to comply with anyregulatory power requirements of the geographical area in which theaircraft has landed.
 15. A system according to claim 14, wherein saidground data link unit further comprises a controller and memory filehaving a record of a plurality of geographical areas and an emittedpower level to be used with each respective geographical area.
 16. Asystem according to claim 14, wherein said ground data link unit furthercomprises a controller and memory file having a record of a plurality ofgeographical areas and a respective sub-band frequency channel to beused for each respective geographical area.
 17. A system according toclaim 14, and further comprising an airport based archival data storecoupled to said airport based spread spectrum receiver that receives andstores said flight performance data.
 18. A system according to claim 17,and further comprising a wireless router that couples said airport basedspread spectrum receiver to said airport based archival data store. 19.A system according to claim 14, and further comprising an airport basedserver coupled to said airport based spread spectrum receiver forreceiving flight performance data from the airport based spread spectrumreceiver.
 20. A system according to claim 14, and further comprising aremote flight operations center operatively coupled to said airportbased server for receiving and processing the retrieved flightperformance data.
 21. A system according to claim 14, wherein the spreadspectrum communication signal comprises a direct sequence spreadspectrum signal.
 22. A system according to claim 14, wherein the spreadspectrum communication signal comprises a signal within the S band. 23.A system according to claim 14, wherein the spread spectrumcommunication signal comprises a signal within the range of about 2.4 toabout 2.5 GHz.
 24. A system according to claim 14, wherein said archivaldata store of said ground data link unit further comprises means forcompressing said flight performance data during the flight of theaircraft.
 25. A system for exchanging information to and from anaircraft comprising:a ground data link unit that obtains flightperformance data representative of aircraft flight performance duringflight of the aircraft, said ground data link unit comprising:a) anarchival data store operative to accumulate and store flight performancedata during flight of the aircraft, and b) a spread spectrum transceivercoupled to said archival data store, and comprising a transmitter thatis operative after the aircraft completes its flight and lands at anairport to download said flight performance data that has beenaccumulated and stored by said archival data store during flight overone of a plurality of sub-band frequency channels of a spread spectrumcommunication signal, wherein said sub-band frequency channel is chosenbased on a position of the aircraft determined by an on board globalpositioning system in order to comply with any regulatory frequencyrequirements of the geographical area in which the aircraft has landed,and a receiver for receiving uploaded data over a second spread spectrumcommunication signal; and an airport based spread spectrum transceivercomprising a receiver that receives the spread spectrum communicationsignal from the aircraft and demodulates the signal to obtain the flightperformance data, and a transmitter that transmits data for uploading tothe aircraft over a second spread spectrum communication signal.
 26. Asystem according to claim 25, wherein the data to be uploaded to anaircraft further comprises video, audio and flight information that hasbeen stored within said airport based archival data store.
 27. A systemaccording to claim 25, wherein the video, audio and flight informationto be uploaded to said aircraft further comprises digitized in-flightpassenger service and entertainment video and audio files.
 28. A systemaccording to claim 25, wherein said ground data link unit furthercomprises an adaptive power control unit that varies the emitted powerlevel of the spread spectrum communication signal based on the positiondetermined by the on board global positioning system in order to complywith any regulatory power requirements of the geographical area in whichthe aircraft has landed.
 29. A system according to claim 28, whereinsaid ground data link unit further comprises a controller and memoryfile having a record of a plurality of geographical areas and an emittedpower level to be used with each geographical area.
 30. A systemaccording to claim 25, wherein said ground data link unit furthercomprises a controller and memory file having a record of a plurality ofgeographical areas and a respective sub-band frequency channel to beused for each geographical area.
 31. A system according to claim 25, andfurther comprising an airport based archival data store coupled to saidairport based spread spectrum receiver that receives and stores saidflight performance data.
 32. A system according to claim 25, and furthercomprising a wireless router that couples said airport based spreadspectrum receiver to said airport based archival data store.
 33. Asystem according to claim 25, and further comprising an airport basedserver coupled to said airport based spread spectrum receiver forreceiving flight performance data from the airport based spread spectrumreceiver.
 34. A system according to claim 25, and further comprising aremote flight operations center operatively coupled to said airportbased server for receiving and processing the retrieved flightperformance data.
 35. A system according to claim 25, wherein the spreadspectrum communication signal comprises a direct sequence spreadspectrum signal.
 36. A system according to claim 25, wherein the spreadspectrum communication signal comprises a signal within the S band. 37.A system according to claim 25, wherein the spread spectrumcommunication signal comprises a signal within the range of about 2.4 toabout 2.5 GHz.
 38. A system according to claim 25, wherein said archivaldata store of said ground data link unit further comprises means forcompressing said flight performance data during the flight of theaircraft.
 39. A method of providing a retrievable record of the flightperformance of an aircraft comprising the steps of:collecting datawithin a ground data link unit on the flight performance of the aircraftduring flight of the aircraft; accumulating and storing within anarchival memory of the ground data link unit the flight performance dataduring flight of the aircraft; determining the position of the aircraftbased on a global positioning system situated on the aircraft; after theaircraft lands at an airport at completion of the flight, selecting asub-band frequency channel based on the determined position of theaircraft to comply with any regulatory frequency requirements of thegeographical area in which the aircraft has landed; downloading theflight performance data that has been accumulated and stored during theflight over the selected sub-band frequency channel of a spread spectrumcommunication signal to an airport based spread spectrum receiver; anddemodulating within the receiver the received spread spectrum signal toobtain the flight performance data.
 40. A method according to claim 39,and further comprising the step of varying the emitted power level ofthe spread spectrum communication signal based on the positiondetermined by the global positioning system in order to comply with anyregulatory power requirements of the geographical area in which theaircraft has landed.
 41. A method according to claim 39, and furthercomprising the step of storing the demodulated flight performance datawithin an airport based archival data store.
 42. A method according toclaim 39, and further comprising the step of retrieving the flightperformance data via an airport based server for further processing. 43.A method according to claim 39, wherein the spread spectrumcommunication signal comprises a direct sequence spread spectrum signal.44. A method according to claim 39, wherein the spread spectrumcommunication signal comprises a signal within the S band.
 45. A methodaccording to claim 39, wherein the spread spectrum communication signalcomprises a signal within the range of about 2.4 to about 2.5 GHz.
 46. Amethod according to claim 39, and further comprising the step ofcompressing the flight performance data within the archival memorystorage during flight of the aircraft.
 47. A method according to claim39, and further comprising the step of routing the flight performancedata from an airport based processor and archival data store via a firstground based spread spectrum transceiver via a first spread spectrumcommunication signal to a ground based spread spectrum transceiverfunctioning as a repeater to relay the flight performance data to theaircraft via a second spread spectrum communication signal.